Láncolt lista példa

#include <stdio.h>
#include <stdlib.h>

struct NODE {
    int number;
    struct NODE *next;
    };

int search_value(struct NODE *llist, int num);
void append_node(struct NODE *llist, int num);
void display_list(struct NODE *llist);
void delete_node(struct NODE *llist, int num);

int main(void){
    int num = 0;
    int input = 1;
    int retval = 0;
    struct NODE *llist;

    llist=(struct NODE *) malloc(sizeof(struct NODE));
    llist->number = 0;
    llist->next = NULL;

    while(input!=0){
        printf("\n-- Menu Selection --\n");
        printf("0) Quit\n");
        printf("1) Insert\n");
        printf("2) Delete\n");
        printf("3) Search\n");
        printf("4) Display\n");
        scanf("%d", &input);

        switch(input) {
        case 0:
        default:
            printf("Goodbye ...\n");
            input = 0;
            break;

        case 1:
            printf("Your choice: 'Insertion'\n");
            printf("Enter the value which should be inserted: ");
            scanf("%d", &num);
            break;

        case 2:
            printf("Your choice: 'Deletion'\n");
            printf("Enter the value which should be deleted: ");
            scanf("%d", &num);
            delete_node(llist, num);
            break;

        case 3:
            printf("Your choice: 'Search'\n");
            printf("Enter the value you want to find: ");
            scanf("%d", &num);
            if((retval = search_value(llist, num)) == -1)
                printf("Value `%d' not found\n", num);
            else
                printf("Value `%d' located at position `%d'\n", num, retval);
            break;

        case 4:
            printf("Your choice: `Display'\n");
            display_list(llist);
            break;
        }
    }
    free(llist);
    return (0);
}

void display_list(struct NODE *llist){
    while (llist->next != NULL){
        printf("%d", llist->number);
        llist = llist->next;
    }
    printf("%d", llist->number);
}

void delete_node(struct NODE *llist, int num){
    struct NODE *temp;
    temp = (struct NODE *) malloc(sizeof(struct NODE));
    if(llist->number == num){
        temp = llist->next;
        free(llist);
    } else{
        while(llist->next->number != num)
            llist = llist->next;

        temp = llist->next->next;
        free(llist->next);
        llist->next = temp;
    }
}

int search_value(struct NODE *llist, int num){
    int retval = -1;
    int i = 1;
    while(llist->next != NULL){
        if(llist->next->number == num)
            return i;
        else i++;
        llist = llist->next;
    }
    return retval;
}